取得一个NSDate对象的1个或多个部分

NSLog(@"当前时间：%@",[NSDate date]);

NSCalendar *calendar = [NSCalendar currentCalendar];

NSDate *date=[NSDate date];

NSDateComponents *component=[calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit |NSSecondCalendarUnit) fromDate:date];

NSLog(@"%ld",(long)[component year]);

NSLog(@"%ld",(long)[component month]);

NSLog(@"%ld",(long)[component day]);

NSLog(@"%ld",(long)[component hour]);

NSLog(@"%ld",(long)[component minute]);

NSLog(@"%ld",(long)[component second]);

[component weekday]

[component weekOfMonth]

[component weekOfYear]